While tremendous work has gone into spin-orbit torque and spin current generation, charge-to-spin conversion efficiency remains weak in silicon to date, generally stemming from the low spin-orbit coupling (low atomic number, Z) and lack of bulk lattice inversion symmetry breaking. Here we report the observation of spin-orbit torque in an amorphous, non-ferromagnetic FexSi1−x / cobalt bilayer at room temperature, using spin torque ferromagnetic resonance and harmonic Hall measurements. Both techniques provide a minimum spin torque efficiency of about 3 %, comparable to prototypical heavy metals such as Pt or Ta. According to the conventional theory of the spin Hall effect, a spin current in an amorphous material is not expected to have any substantial contribution from the electronic bandstructure. This, combined with the fact that FexSi1−x does not contain any high-Z element, paves a new avenue for understanding the underlying physics of spin-orbit interaction and opens up a new class of material systems - silicides - that is directly compatible with complementary metal-oxide-semiconductor (CMOS) processes for integrated spintronics applications.
@article{arxiv.2006.07786,
title = {Spin-orbit torque generated by amorphous Fe$_{x}$Si$_{1-x}$},
author = {Cheng-Hsiang Hsu and Julie Karel and Niklas Roschewsky and Suraj Cheema and Dinah Simone Bouma and Shehrin Sayed and Frances Hellman and Sayeef Salahuddin},
journal= {arXiv preprint arXiv:2006.07786},
year = {2020}
}